The present invention relates to copolymers, processes for their preparation, mixtures and concentrates containing them and mineral oil middle distillate compositions and their use as flow improvers and paraffin dispersants.
Middle distillates, such as gas oils, diesel oils and heating oils, which are obtained from mineral oil by distillation, have different contents of paraffins, depending on the origin of the crude oil. Precipitation of solid paraffins occurs at low temperatures. The term cloud point (CP) of the raffinate is used. On further cooling, the lamellar n-paraffin crystals form a house-of-cards structure which leads to setting of the middle distillate although the predominant part of the middle distillate is still liquid. The flowability of the mineral oil distillate fuels is considerably impaired by the precipitated n-paraffins in the temperature range between cloud point (CP) and pour point. The paraffins block filters and result in nonuniform or no fuel feed to the combustion units. Similar faults occur in the case of heating oils.
It has long been known that the crystal growth of the paraffins in the mineral oil middle distillates, combustion fuels and power fuels can be modified by suitable additives. Effective additives prevent the paraffins from forming such house-of-cards structures in the middle distillates and from becoming solid at temperatures only a few degrees Celsius below the temperature at which the first paraffin crystals crystallize out. Instead, fine, well crystallized, separate paraffin crystals are formed, said crystals passing through filters in motor vehicles and heating installations or at least forming a filter cake which is permeable for the liquid part of the middle distillates, so that trouble-free operation is ensured.
Depending on the origin of the crude oil and on the refinery cut, there are however middle distillates in which conventional flow improvers exhibit insufficient response if any at all.
A further disadvantage of conventional flow improvers is based on the fact that, owing to their density being higher than the liquid part, the precipitated paraffin crystals tend increasingly to settle out on the bottom of the container during storage. This results in the formation of a homogeneous low-paraffin phase in the upper part of the container and of a two-phase paraffin-rich layer at the bottom. Since, both in vehicle tanks and in storage or delivery tanks of the mineral oil dealers, the middle distillate is generally withdrawn slightly above the bottom of the container, there is a danger that the high concentration of solid paraffins will lead to blockages of filters and metering means. This danger is all the greater the further the storage temperature falls below the cloud point of the middle distillate, since the amount of precipitated paraffin increases with decreasing temperature.
The mode of action of the conventional flow improvers and paraffin dispersants is based on the modification of the paraffin crystals. These are generally polymers which change the crystal growth of the n-paraffins by cocrystallization (interaction) and thus improve the flow properties of the middle distillate at low temperatures. According to DIN EN 116, the efficiency of the flow improvers is expressed indirectly by measurement of the Cold Filter Plugging Point (CFPP).
Ethylene/vinyl carboxylate copolymers, as disclosed, for example, in U.S. Pat. Nos. 3,048,479 and 3,627,838, have long been used as flow improvers.
WO 95/25755 describes flow improvers based on a copolymer of diketene, unsaturated dicarboxylic acids and olefins.
It is an object of the present invention to provide flow improvers and paraffin dispersants which are effective also in critical mineral oil middle distillates in which conventional flow improvers exhibit insufficient response if any at all.
We have found that this object is achieved, according to the invention, by providing a copolymer of the monomers of the following components A to C and, if required, D, the total amount by weight of which is 100 mol %:
a: from 20 to 80 mol % of at least one ethylenically unsaturated dicarboxylic acid or of an anhydride, ester and/or amide thereof as component A,
b: from 1 to 79 mol % of at least one diketene of the general formula (I) 
xe2x80x83where R1 and R2 independently are each hydrogen or C1-C30-alkyl, as component B,
c: from 1 to 79 mol % of at least one vinyl ester, alkyl (meth)acrylate, (meth)acrylonitrile or mixtures thereof as component C and
d: from 0 to less than 0.5 mol % or, if at least 20 mol % of component C are present, from 0 to 20 mol % of at least one further olefinically unsaturated monomer as component D.
Certain copolymers which resemble the novel copolymers are known. Copolymers of maleic anhydride, diketene and a vinyl ether are disclosed in DE-A-25 31 194. They are used as surface-active compounds, glass cleaners or builders for solid and liquid synthetic detergents.
DE-A-25 31 195 discloses similar copolymers which are based on maleic anhydride and diketene and, if desired, vinyl ethers. They are used for the antistatic treatment of organic fiber materials or as care agents for color fabrics.
DE-A-39 13 127 discloses copolymers of maleic anhydride, diketene and (meth)acrylic acid. They are used as additives in pulverulent or liquid detergents and cleaning agents.
The components of the novel copolymers are described below.
Component A is used in the novel copolymers in an amount of from 20 to 80, preferably from 20 to 70, in particular from 25 to 68, mol %.
Preferably used components A are compounds of the general formula (II)
R4xe2x80x94OCxe2x80x94R3Cxe2x95x90CR5xe2x80x94COxe2x80x94R6xe2x80x83xe2x80x83(II)
where R3 and R5 independently are each hydrogen or C1-C22-alkyl, preferably C1-C10-alkyl, in particular C1-C6-alkyl, and
R4 and R6 independently are each hydrogen or a radical of an NH-, SH- and/or OH-functional compound, in particular hydrogen, xe2x80x94SR7, xe2x80x94OR8 or xe2x80x94NR9R10,
or, in the case of cis-dicarboxylic acid compounds, R4 and R6 together are xe2x80x94Oxe2x80x94 or xe2x80x94NR11xe2x80x94 and R7 to R11 independently are each C1-C22-, preferably C1-C10-, in particular C1-C6-alkyl or -hydroxyalkyl or C2-C22-alkenyl, preferably C2-C10-alkenyl, in particular C2-C6-alkenyl, each of which may be interrupted by up to 3 oxygen atoms and/or aminoalkylated, or a polyether radical or polyamine radical.
If R4 and R6 together form a radical xe2x80x94Oxe2x80x94, resulting compounds are acid anhydrides.
Examples of suitable components A are monoethylenically unsaturated dicarboxylic anhydrides of 4 to 8 carbon atoms, such as maleic anhydride, itaconic anhydride, mesaconic anhydride, citraconic anhydride and methylenemalonic anhydride. Among the stated anhydrides, maleic anhydride and itaconic anhydride are preferably used, in particular maleic anhydride.
Dicarboxylic acids, such as fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, methylenemalonic acid and their corresponding mono- and dialkyl esters with, preferably, C1-C12-alcohols, in particular aliphatic linear C1-C6-alcohols, are furthermore preferred.
The NH- and/or OH-functional compounds may be of the general formula (IV)
Axe2x80x94[CHR14xe2x80x94CHR15xe2x80x94O]m[CHR16xe2x80x94(CH2xe2x80x94)xNHxe2x80x94]nHxe2x80x83xe2x80x83(IV)
where m is from 0 to 100, preferably from 0 to 50, in particular from 0 to 20,
n and x are each from 0 to 5,
R14, R15 and R16 independently are each hydrogen or C1-C6-alkyl and
A is C2-C30-alkoxy, preferably C2-C20-alkoxy, in particular C2-C10-alkoxy, especially C2-C6-alkoxy, or NR17R18, where one of the radicals R17 and R18 may be hydrogen and at least one of the radicals R17 and R18 differs from hydrogen and is C1-C30-alkyl, preferably C1-C20-alkyl in particular C1-C6-alkyl or C2-C30-alkenyl, preferably C2-C20-alkenyl, in particular C2-C6-alkenyl, or xe2x80x94[CHR19xe2x80x94CHR20xe2x80x94Oxe2x80x94]pH, R19 and R20 independently each being hydrogen or C1-C6-alkyl and p being from 1 to 100, preferably from 1 to 50, in particular from 1 to 20.
The values of m, n and p may also be average values if there is a distribution of the amount of these building blocks.
The compound of the general formula (IV) is preferably reacted at the bond which leads to the hydrogen atom on the right.
The novel copolymers contain from 1 to 79, preferably from 10 to 60, in particular from 10 to 53, mol % of component B. In the compounds of the general formula (I), R1 and R2, independently of one another, are each hydrogen or C1-C30-alkyl, preferably C1-C20-alkyl, particularly preferably C1-C10-alkyl especially C1-C6-alkyl. An example of a substituted diketene is the distearyldiketene which is sold under the name Basoplast(copyright) by BASF and where R1 and R2 are each of 14 to 16 carbon atoms. The unsubstituted diketene (R1 and R2 are each H) is preferably used.
The novel copolymers contain from 1 to 79, preferably from 20 to 70, in particular from 22 to 65, mol % of component C. Preferably used components C are vinyl esters of aliphatic C1-C6-carboxylic acids, alkyl (meth)acrylates with aliphatic C1-C12-alcohols, preferably C1-C6-alcohols, (meth)acrylonitrile or mixtures thereof. Vinyl esters of aliphatic C1-C5-carboxylic acids and/or (meth)acrylonitrile are particularly preferably used. In particular, vinyl acetate and/or vinyl propionate are used.
The novel copolymers contain from 0 to less than 0.5 mol % or, if at least 20 mol % of component C are present, from 0 to 20, preferably from 0 to 10, in particular from 0 to 5, mol % of at least one further olefinically unsaturated monomer. Particularly preferably, no component D is present. If an additional component D is used, it preferably comprises at least one compound of the general formula (III)
H2Cxe2x95x90CR12R13xe2x80x83xe2x80x83(III)
where R12 is hydrogen or C1-C12-alkyl, preferably C1-C6-alkyl, and R13 is hydrogen, C1-C12-alkyl, preferably C1-C6-alkyl, C2-C12-alkenyl, preferably C2C6-alkenyl, or C6-C12-aryl, preferably phenyl.
In order to obtain a very advantageous effect of the novel copolymers as flow improvers, the amount of component D should be kept small. In particular, no component D is used.
Monomer combinations comprising maleic anhydride, diketene and vinyl acetate or vinyl propionate are particularly preferably used. Furthermore, monomer mixtures comprising C12/14-dialkylfumaric esters and/or C16/18-dialkylfumaric esters and/or C18/22-dialkylfumaric esters, diketene and vinyl acetate or vinyl propionate are preferably used.
Preparation of the Copolymers
For the preparation of the copolymers, the monomers of components A to C and, if desired, D are reacted in the abovementioned ratio in the presence of a free radical polymerization initiator.
It is also possible to carry out the copolymerization of the monomers by a procedure in which, in a first step, at least one ethylenically unsaturated carboxylic acid or an anhydride or ester thereof is used as component A and, in a second step, the copolymer obtained is reacted with an OH- and/or NH-functional compound, as described above in the general formula (IV).
The polymerization of the components A, B, C and, if desired, D is carried out in general in a manner known per se in inert organic solvents under free radical conditions (cf. DE-A-23 42 300 or DE-A-25 31 135). Particularly suitable solvents are those which prac-tically do not intervene in the polymerization and do not react with the monomers. Such solvents, which may be used alone or as a mixture, are, for example, acetone, methyl ethyl ketone, diethyl ketone, cyclohexanone, tetrahydrofuran dioxane, ethyl acetate, ethyl propionate, aromatic hydrocarbons, such as benzene, toluene, xylene, cumene, tetralin and solvent naphtha (e.g. Solvesso(copyright) 150), aliphatic hydrocarbons, such as pentane, hexane, heptane, octane, isooctane, cyclohexane, decalin and Shellsol(copyright) D 70, and halogenated, aliphatic hydrocarbons, such as dichloromethane, dichloroethane and trichloroethane.
Solvesso(copyright) 150 is Exxon Chemical GmbH""s name for an aromatic solvent fraction boiling within the range from 187 to 203xc2x0 C. It contains about 99% of aromatics. Shellsol(copyright) D 70 is Shell""s name for a dearomatized, aliphatic hydrocarbon mixture boiling within the range from 195 to 245xc2x0 C.
A preferably used solvent is acetone, methyl ethyl ketone, toluene, xylene, tetralin, decalin, solvent naphtha (such as Solvesso(copyright) 150) or Shellsol(copyright) D 70.
The copolymerization of the components A, B, C and, if desired, D is carried out as a rule in the presence of compounds which decompose into free radicals under the polymerization conditions. Suitable polymerization initiators of this type are, for example, hydrogen peroxide, organic peroxides and hydroperoxides, azo compounds and peroxodisulfates. The polymerization can also be carried out by the action of high-energy radiation or by irradiation of the reaction mixture in the presence of a photoinitiator, such as benzoin.
Initiators should preferably have a half-life of  less than 10 hours at the chosen polymerization temperatures. Preferably used polymerization initiators are tert-butyl perpivalate, dilauryl peroxide, tert-butyl per-2-ethylhexanoate (butyl peroctanoate), tert-butyl perbenzoate, dicumyl peroxide, di-tert-butyl peroxide, 2,2xe2x80x2-azobis(2-methylpropionitrile) or mixtures thereof. The half-lives of the stated peroxides can be reduced by the presence of redox coinitiators, such as benzoin or dimethylaniline, and of organic soluble complexes or salts of heavy metals, such as copper, cobalt, manganese, iron, nickel or chromium.
The polymerization initiators which decompose into free radicals are used in conventional amounts, such as from 0.1 to 5.0 mol %, based on the total weight of the monomers used in the polymerization.
The polymerization can, if desired, be carried out in the presence of conventional regulators, such as mercaptoethanol, mercaptopropanol, mercaptoacetic acid, mercaptopropionic acid, thiolactic acid, n-butyl mercaptan, tert-butyl mercaptan, octyl mercaptan and dodecyl mercaptan. Further suitable regulators are aldehydes, such as acetaldehyde, propionaldehyde, butyraldehyde, formic acid and buten-1-ol.
The polymerization is preferably carried out in stirred kettles which are equipped, for example, with an anchor stirrer, paddle stirrer or impeller stirrer. The copolymerization can be carried out, for example, as a solution, precipitation or suspension polymerization.
In the case of the precipitation and suspension polymerization, it may be advantageous to carry out polymerization additionally in the presence of protective colloids. Suitable protective colloids are, for example, copolymers of maleic anhydride and vinyl alkyl ethers which carry 1 to 20 carbon atoms in the alkyl radical or copolymers of maleic anhydride, monoesters thereof with C10-C30-alcohols or monoamides with C10-C20-amines and olefins of 8 to 30 carbon atoms. Polyalkyl vinyl ethers whose alkyl group contains 1 to 20 carbon atoms, such as polymethyl, polyethyl and polyisobutyl vinyl ether, are also suitable. If a protective colloid is used in the copolymerization, the effective amounts are from 0.05 to 4.0 mol %, based on the monomers A, B, C and, if desired, D to be polymerized.
The concentration of the monomers in the inert organic solvents is in general from 5 to 80, preferably from 15 to 60, mol %. The polymerization temperature is as a rule from 40 to 160xc2x0 C., preferably from 50 to 150xc2x0 C.
After the end of the polymerization, the copolymers can be isolated, for example by distilling off the solvent used in the polymerization or by precipitating the copolymers with a suitable solvent. The copolymers then remain as a powder residue.
The weight average molecular weight of the novel copolymers is in general from 300 to 50,000, preferably from 600 to 20,000.
Modification of the Copolymers
The copolymers can be used as such in mineral oil middle distillates or can be first completely or partially modified by polymer-analogous reactions.
The novel copolymers contain, as reactive groups, in particular carboxyl, anhydride, ester and 4-ring lactone structural units. In addition to simple hydrolysis with water, reactions with NH-, SH- and OH-functional compounds are also advantageous. Apart from the direct esterification of carboxylic acid, anhydride or lactone units, the transesterification of carboxylic ester units based on lower alcohols with longer-chain alcohols is also possible here.
Suitable reactants are, for example, those of the above formula (IV), as well as alcohols, phenols, mercaptans, oximes, imines and primary and secondary amines. The reaction of the copolymers can be carried out here in the organic solvent in which the copolymerization was also carried out, or the solvents used are first distilled off and the corresponding reactions then carried out.
The alcohols used may be in particular branched or straight-chain C1-C30-alkyl alcohols or alkenyl alcohols, preferably C10-C30-alkyl or alkenyl alcohols, such as decanol, dodecanol, isotridecanol, tetradecanol, stearyl alcohol, tallow fatty alcohol or behenyl alcohol.
Alkoxylates of alcohols, amines, amides or carboxylic acids may also be used, such as alkoxylation products of distearylamine, oleylamine, di-coconut fatty amine, aminopropylstearylamine, di-tallow fatty amine, hydrogenated di-tallow fatty amine, stearyl alcohol, isotridecanol, isotridecylamine and behenyl alcohol.
The amines used may be primary or secondary C1-C10-alkylamines, preferably C1-C6-alkylamines, polyetheramines or polyamines.
Examples of primary or secondary amines are isotridecylamine, stearylamine, coconut fatty amine, distearylamine, di-tallow fatty amine, dioleylamine and di-coconut fatty amine. It is also possible to use polyamines, such as aminopropylstearylamine, aminopropyllaurylamine, N,N-dimethylpropylenediamine or N,N-dimethyldipropyltriamine. Other suitable amine components are aminopropylated alcohols, aminated alkoxylates or aminopropylated alkoxylates, such as aminopropylstearyl alcohol, aminopropylethoxystearylamine, fatty alkyl polyethylene glycol amine (such as aminated Lutensol(copyright) brands from BASF Aktiengesellschaft).
The reaction of the novel copolymers with alcohols and/or amines or derivatives thereof is carried out in the absence of a solvent or in those solvents which in general themselves contain no acidic hydrogen atoms. It is possible to use the same solvents as in the polymerization. The reaction need not go to completion. The amido, imido and ester groups formed during the reaction and the decrease in the 4-ring lactone and possibly in the carboxylic anhydride units can be monitored by IR spectroscopy. Where the novel copolymers contain car-boxyl or anhydride functions, a decrease in the acid number [mg KOH/g] may be observed simultaneously.
Based on their convertible OH or NH equivalents, the alcohol or amine component is usually used in amounts from 0.1 to 3 equivalents per equivalent of carboxylic acid groups in the polymerized amount of dicarboxylic acid or dicarboxylic acid derivative and/or polymerized lactone units. Amounts of from 0.5 to 2 equivalents of NH or OH functions per reactive center in the novel copolymer are preferred.
Copolymers based on ethylenically unsaturated dicarboxylic esters, diketene and vinyl esters or corresponding reaction products of the resulting novel polymers with n-alkyl alcohols, such as dodecanol, tetradecanol, stearyl alcohol, behenyl alcohol or mixtures of alcohols having different alkyl chain lengths and with primary and secondary alkyl- or alkyleneamines have proven particularly advantageous flow improvers for middle distillates.
The novel, unmodified or modified copolymers are used as additives for mineral oil middle distillates, which are understood as meaning petroleum, light heating oil and diesel fuels having a boiling point of from about 150 to 400xc2x0 C. The copolymers may be added to the middle distillates directly but are preferably added as a 20 to 70 mol % solution. Suitable solvents are aliphatic or aromatic solvents, such as toluene, xylene, decalin and mixtures thereof, as well as high-boiling mixtures of aromatics and/or mixtures of aliphatics, and mineral oil middle distillates. The amount of copolymers in the mineral oil middle distillates is as a rule from 10 to 10,000, preferably from 20 to 5000, particularly preferably from 50 to 1000, ppm.
Depending on the intended use, the mineral oil middle distillates may contain further additives, such as flow improvers, paraffin dispersants, antifoams, corrosion inhibitors, antioxidants, emulsifiers, lubricity additives, detergents, cetane number improvers, conductivity improvers and/or dyes.
Combinations of different flow improvers and/or paraffin dispersants are often used in mineral oil middle distillates. Suitable co-active ingredients are, for example, ethylene/vinyl ester copolymers, as described in DE-A-19 14 756 and EP-A-0 486 836, and/or xcex1-olefin/maleic ester copolymers (EP-A-0 214 876) and/or alkyl fumarate/vinyl acetate copolymers (EP-B-0 153 176).
However, copolymers which are equally suitable as co-active ingredients are those which also contain further comonomers in addition to ethylene, vinyl esters and/or unsaturated mono- and/or dicarboxylic esters. The molecular weight (Mw) of these flow improvers is as a rule from 500 to 50,000, preferably from 1000 to 20,000.
In mineral oil middle distillates, regardless of their origin, the novel copolymers in combination with conventional flow improvers based on ethylene/vinyl carboxylate copolymers result in a substantial improvement in the low-temperature flow properties by virtue of the fact that they modify the crystal shape and crystal size in such a way that there are no blockages of filters and fines by paraffin crystals.
It has been found that, particularly in critical middle distillates in which conventional flow improvers alone are not sufficiently effective, the addition of the novel copolymers in combination with conventional flow improvers based on ethylene/vinyl carboxylate copolymers leads to substantially improved cold flow behavior (decrease in CFPP) of the middle distillates.
The present invention therefore relates to a mixture of 5 to 95% by weight of at least one copolymer as described above and from 5 to 95% by weight of at least one ethylene/vinyl carboxylate copolymer. The mixture may, if required, be dissolved in a solvent as mentioned above. Both the copolymers and the mixtures, if desired as a 20 to 70 mol % solution in a solvent, may be used as an additive for mineral oil middle distillates, in particular as flow improvers or paraffin dispersants.
The present invention also relates to a corresponding concentrate containing from 20 to 70% by weight of at least one copolymer as described above and/or of a mixture as described above, dissolved in a solvent.
The present invention furthermore relates to a mineral oil middle distillate containing at least one copolymer as described above and/or a mixture as described above and/or a concentrate as described above.